High-voltage power switch with a field electrode

ABSTRACT

High-voltage power switch including a first and a second contact piece that form an air gap in the switched-off state, a compression piston that surrounds the first contact piece, a drivable compression cylinder that surrounds the second contact piece in the switched-on state, and a first field electrode that surrounds the second contact piece in the switched-off state and is axially movable in relation thereto. The high-voltage power switch also provides that the first field electrode is insulated from the compression cylinder and axially movable in relation thereto and the compression cylinder is displaced by a distance from the second contact piece in the switched-off state.

FIELD OF THE INVENTION

The present invention relates to a high-voltage power switch.

BACKGROUND INFORMATION

A conventional high-voltage power switch is described in GermanApplication No. 21 40 284. In this power switch, a field electrode isembedded in the compression cylinder. Due to the fact that thecompression cylinder extends into the gap in a switched-off position,the gap is exposed to a high dielectric load through this fieldelectrode.

In another conventional high-voltage power switch described in GermanApplication No. 42 17 232, a first field electrode is formed by a bottomof the movable compression cylinder. In the switched-off state, thecompression cylinder bridges the gap, so that the compression cylinderbottom (configured as a field electrode) coaxially surrounds one of thecontact pieces in a switched-off state, while the fixed compressionpiston surrounds the other contact piece.

It is disadvantageous, especially in the case of very high voltages, tohave the gap bridged by one insulating solid body, as in the case ofknown devices.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a high-voltage powerswitch, wherein, on the one hand, field electrodes are provided aroundthe gap area to make the electric field more uniform and, on the otherhand, the gap has the highest possible dielectric strength in theswitched-off state.

This object is achieved according to the present invention byconfiguring the compression piston as a second field electrode and thecompression piston is drivable in the direction of the second contactpiece.

A high-voltage power switch according to the present invention includesfirst and second contact pieces that delimit an air gap in theswitched-off state, a compression piston that surrounds the firstcontact piece, a drivable compression cylinder that surrounds the secondcontact piece in the switched-on state, and a first field electrode thatsurrounds the second contact piece in the switched-off state and isaxially movable in relation thereto. The first field electrode isseparate from the compression cylinder and axially movable in relationthereto. The compression cylinder is positioned at a predefined distancefrom the second contact piece in the switched-off state. In addition,the first field electrode is spring-loaded axially in the direction ofthe compression cylinder, with a stop being provided which limits themotion of the first field electrode toward the gap.

By separating the first field electrode from the compression cylinder,the latter can be removed from the second contact piece duringswitch-off so that it does not bridge the gap in the switched-offposition. Starting at the time when the compression cylinder isseparated from the second contact piece, at the latest, the first fieldelectrode can be brought into the electrically most advantageousposition in the area of the second contact piece.

In the switched-on position, the first field electrode can then be movedaxially to make space for the compression cylinder. Thus, in theswitched-off state, an optimum dielectric strength of the gap isobtained, without hindering the motion of the compression cylinder.

The spring load represents the drive for the field electrode. During theswitching-off process the field electrode follows the compressioncylinder when the latter is withdrawn until the field electrode reachesthe stop limiting its motion and determining its end position.

When the switch is switched on, the compression cylinder is pushedforward. The compression cylinder pushes back the first field electrodeagainst the spring force until the end position of the compressioncylinder is reached.

The compression piston (configured as a second field electrode)surrounds the first contact piece, so that in the switched-off stateeach of the contact pieces is surrounded by a field electrode. Thus asymmetrical configuration of the electric field is obtained in relationto the gap, which increases the dielectric strength of the gap.

Another advantageous embodiment of the present invention provides thatthe axial projections of the front surfaces of the first field electrodeand of the compression cylinder at least partially overlap.

The first field electrode and the compression cylinder can, for example,have the same or similar outer diameters, so that the entire powerbreaker unit can be arranged in a compact manner in relation to itsdiameter.

The inner diameter of the field electrode can be selected, for example,so that it is slightly larger than the outer diameter of the secondcontact piece, so that the second contact piece represents a guide forthe axial motion of the first field electrode at the same time.

The first field electrode can also be advantageously connected to atelescoping rod, which serves as a spring guide for a compression springcausing the first field electrode to move axially. This is an especiallysimple design for providing spring loading of the field electrode in thedirection of the gap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the power switch according to the present invention in aswitch-on state.

FIG. 2 shows the power switch illustrated in FIG. 1 during aswitching-off motion.

FIG. 3 shows the power switch illustrated in FIGS. 1 and 2 in theswitch-off position.

DETAILED DESCRIPTION

The power switch according to the present invention is illustrated inthe FIGS. 1-3, showing the first contact piece 1, the second contactpiece 2, as well a compression piston 3 and a compression cylinder 4,driven by a drive means (not illustrated). All illustrated components ofthe power switch are rotationally symmetrical in relation to the centralaxis of contact pieces 1 and 2. For simplicity's sake, only the upperhalf of the device is shown.

In the switched-on state, compression cylinder 4 bridges the gap betweencontact pieces 1 and 2. A bridge contact 5, consisting of individualcontact plates arranged peripherally in relation to a cylinder, isfirmly connected to compression cylinder 4. The contact plates aresupported radially outward against a support tube 7 through springs 6.

Both the bridging contact 5 and the support tube 7 of compressioncylinder 4 and turbulence grid 8 are moved to the right during theswitching-off process illustrated in FIG. 1. At this time, bridgingcontact 5 moves away from second contact 2, and interrupts the electriccontact between the first contact 1 and the second contact 2.

As compression cylinder 4 moves to the right, first field electrode 9 ispressed against front face 11 of compression cylinder 4 by the force ofspring 10, and follows compression cylinder 4 for a certain distance.During this motion, a telescoping rod 12, connected to the first fieldelectrode 9 and serving as a guide for spring 10, extends.

FIG. 2 shows compression cylinder 4 in an intermediate position, wherebridging contact 5 has already left second contact 2. Bridging contact5, support tube 7 and springs 6 are not shown in FIGS. 2 and 3 for thesake of clarity.

FIG. 3 shows the switched-off state, where compression cylinder 4 iswithdrawn far out of the gap between first contact 1 and second contact2. The volume between compression piston (configured as a second fieldelectrode) 3 and compression cylinder 4 has diminished during theswitching-off process so that the compressed extinguishing gas waspressed out of this volume through turbulence grid 8 into the spacebetween first contact 1 and second contact 2 to extinguish an arc there.Compression cylinder 4 consists of an insulating material, so that itonly affects the dielectric strength of the gap slightly. Compressionpiston 3, consisting of a conducting material, acts as a field electrodeand makes the field around first contact 1 uniform.

First field electrode 9 follows compression cylinder 4 during theswitching-off process, until stop 13 limits the motion of fieldelectrode 9 and determines its position in the switched-off state. Inthis position, first field electrode 9 makes the electric field in thearea of second contact 2 uniform.

The arrangement consisting of contacts 1 and 2, and the two fieldelectrodes 3 and 9, results in a uniform electric field between thecontacts and thus in a higher dielectric strength of the gap.

Stop 13 can also be integrated into telescopic rod 12, for example.

What is claimed is:
 1. A high-voltage power switch, comprising:a firstcontact and a second contact with a gap therebetween; a movablecompression cylinder surrounding the second contact in a switched-onstate, the movable compression cylinder being positioned at a predefineddistance from the second contact in the switched-off state; a firstfield electrode surrounding the second contact and being axially movablerelative to the second contact, the first field electrode beinginsulated from the movable compression cylinder and being axiallymovable relative to the movable compression cylinder, the first fieldelectrode being axially spring-loaded toward the compression cylinder; acompression piston configured as a second field electrode, the secondfield electrode coupled to the movable compression cylinder andsurrounding the first contact, the second field electrode moving inconjunction with the movable compression cylinder; and a stop memberlimiting a movement of the first field electrode toward the gap, whereinthe movable compression cylinder and the second field electrode aredrivable toward the second contact.
 2. The high-voltage power switchaccording to claim 1, wherein the first field electrode includes a firstfront surface, wherein the movable compression cylinder includes asecond front surface, and wherein the first and second surfaces overlap.3. The high-voltage power switch according to claim 1, furthercomprising:a compression spring; and a telescoping rod connected to thefirst field electrode, the telescoping rod guiding an axial movement ofthe compression spring, which spring biases the first field electrodetoward the movable compression cylinder.